Parking brakes for heavy duty construction and off road equipment have been relatively expensive. This was due to the elaborate mounting structures required which were both expensive, lacked durability and corrosion resistance. These previous designs, except for the very high and expensive ones, have also lacked environmental and corrosion protection in their actuation mechanism.
The desire in any disc brake system is to apply the brake force to the disc on demand and to release this clamp force completely on demand. In single acting caliper brakes, those that apply their clamping force from one side of the caliper and allow the brake housing to freely float into contact with the disc, release is always a problem. The actuator is released readily as in a retracting hydraulic piston but the caliper housing and its caliper side friction material stay in contact with the disc with a force equal to the force it takes to move it on its mounts. With seals this force can be substantial. The force causes the friction pad to continue dragging on the disc resulting in premature pad wear, unwanted noise, unnecessary heat and vehicle energy loss.